Fluid balance in patients with acute kidney injury: emerging concepts

Intensive care unit and surgical populations are at increased risk for acute kidney injury (AKI) and oliguria, which often lead to fluid accumulation. Volume resuscitation is a cornerstone in the treatment of hemodynamic instability in these populations. However, fluid balance evaluation and its management in the critically ill can be challenging. Several clinical and paraclinical tools may aid decision-making regarding fluid management. When fluid therapy is indicated, crystalloids should be the preferred agents. Synthetic colloids have been associated with no survival benefit and increased risk of AKI. There is currently a paradigm shift in which hypervolemia is no longer desirable and is increasingly shown to be detrimental to both renal outcomes and survival. Instead, approaches that aim for neutral and slightly negative fluid balance or 'dry' patients after initial fluid resuscitation are favored. This may be achieved by conservative fluid strategies, diuretics or renal replacement therapy. In this paper, we will review recent findings on the principles of fluid management in AKI, including assessment of fluid need, choice of fluid solutions, influence of fluid overload on outcomes, and some practical issues to achieve fluid balance and minimize complications in patients with AKI.